Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates -to protectin~ a splice in
multi-wire electrical cables, in particular communications
cables, from ingress of water into the splice.
Multi-wire electrical cables comprise a core
containing a plurality of individual insulated wire
conductors, surrounded by an outer sheath. The cable core
can contain frcm a few pairs of conductors up to several
thousand pairs. The outer sheath generally consists of an
outer plastic jacket surrounding a metallic shield.
Additional inner polymeric layer or layers may be present.
To protect the conductors from water, the interstices
between the individual wire conductors may be filled with
a filling compound, usually a grease based or petroleum
jelly. Cables that are so filled are generally referred
to as "filled" cables and cables that are not filled are
generally referred to as "air core" cables. Air core
cables can be pressurized to prevent ingress of water.
When a splice is made in a cable, the outer
sheath is removed from the end of the cable. At least
some of the individual wire conductors in the core of the
cable are joined to conductors of another cable or
cables. After completion of the splice, the entire splice
area, that is the area of the cables where the sheath has
been removed, must be protected. Generally, an enclosure
or splice case is placed over the area. A preferred
enclosure is a dimensionally recoverable polymeric
sleeve, preferably a heat-shrinkable polymeric sleeve.
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An inner protective casing or lining may be pQsitioned
about the splice before installation of the sleeve to
provide additional mechanical protection. Molded plastic
or lead splice cases are also used.
The splice case can be filled with a suitable
filling compound to protect the individual wire conductors
in the core of the splice (referred to herein as the
splice bundle or splice core). Such filling compounds can
be curable liquid polymer systems or grease-like materials,
generally based on petroleum jelly. Curable liquid
polymer systems are ùsed by pouring a curable liquid
sealant into a splice case positioned about the splice and
allowing it to cure. Particularly useful curable liquid
sealants are two-part polyurethane systems comprising
a prepolymer and a curing agent or hardener. When cured
the filling compound solidifies, preferably to a gel-like
consistency, forming a protective layer around the splice.
It has been found that this technique doesn't adequately
protect the ~splice from ingress of water, particularly if
one of the cables contains 400 pairs or more of wire
conductors. Seepage of water into the splice eventually
causes electrical failure of the joined conductors.
It has been discovered that a splice in
multi-wire electric cables can be protectèd from water
ingress if a curable liquid sealant is placed in a flexible
reservoir surrounding the splice and subjected to compression
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while it is in the liquid state and maintained under compression
for a time sufficient to permit cure of the liquid sealant to its
hardened state.
There has been proposed in a brochure of Pirelli
General, entitle "Resinwrap Joints" of March, 1964, a procedure
for providing synthetic joints for plastic and insulated sheath
cables, particularly for joints hav:Lng a considerable free space
internally, which is required to be filled with resin, wherein an
aluminium polyethylene laminate sheet foil is formed around the
joint in envelope fashion, the ends of the envelope are pressed
on the sheath and secured with pvc tape, the top of the envelope
is formed into a pouring hole, and a specified amount of resin is
introduced. The envelope is then compacted by folding and mani-
pulating, thus ~orcing the resin fully into the joint, and~inally, when the envelope has been folded down completely to the
joint surface, it is taped overall with pvc tape, the pvc tape
firstly being an adhesive pvc tape applied without tension, and
the joint being compressed with the hands, and then a further
layer of pvc tape being applled over the joint with maximum ten-
sion. On particularly large joints it is desirable to apply one
layer of cotton tape over the first layer of pvc tape very
tightly to compress the joint, which is then left on and the
final layer of pvc tape applied overall.
However, while such a procedure provides a flexible
reservoir and sub~ects it to compression, such a procedure with
the use of a reservoir formed from aluminium foil laminate, is
subject to a number of disadvantages. In particular, the forma-
tion and subsequent manipulation of the flexible reservoir iscumbersome and time consuming and is not readily usable by the
craftsmen in the field. In particular, it requires a number of
manipulative steps. Further, the aluminium foil on the envelope
being compacted by folding and manipulating to force the resin
into the joint by squeezing, and subsequently using wrapping tape
under tension, particularly using thin film wrapping tape, tends
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to wrinkle and form irregular shapes, and further, aluminium has
high tensile strength, and thus the crushed and wrinkled alu-
minium envelope will tend to puncture and cut the wrapping tape.
Further, the aluminium foil laminate sheet is a relatively expen-
sive material.
It has now been found that the use of a plastic film informing the envelope, such as a nylon film, overcomes all the
above disadvantages in that it is easy to manipulate, does not
require a significant amount of manipulation, and therefore is
readily usable by the craftsmen in the field, does not cut the
wrapping tape, and is relatively inexpensive. However, it has
been further found that a simple plastic film of desirable thick-
ness for optimum flexibllity is not sufficiently strong to sup-
port the weight of the liquid sealant in the reservoir, and thereservoir will tend to bulge during curing and wrapping, giving
the joint an irregular shape which is undesirable, as it is in
many cases desirable to enclose the wrapped taped joint in a con-
ventional splice case of regular shape to protect it against
mechanical damage. It has, however, further been found that this
bulging can be avoided by providing a porous liner adhered to the
inside surface of the reservoir, which liner does not interfere
with the compression of the reservoir, such as a flexible
polymeric open-celled foam sheet, or a corrugated rigid plastic
sheet.
The present invention provides a method of protecting a
splice connecting at least two multi-wire electrical cables from
ingress of water, each of said cables having an outer sheath of
at least two layers of material and an inner core comprising a
plurality of individual insulated wire conductors having inter-
stices therebetween, whlch comprises: (a) positioning a flexible
reservoir about the splice, said reservoir having at least one
opening therein and being sealed at each end thereof to the outer
sheath of the cables adjacent said splice; (b) introducing a cur-
able liquid sealant into said reservoir through said opening and
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then closing said opening; (c) compressing said reservoir thereby
forcing said liquid sealant to penetrate into the core of said
splice and into the core of said cables adjacent said splice; and
(d) maintaining said reservoir under compression for a period o~
time sufficient to permit said liqu:Ld sealant to cure thereby
forming a water impenetrable seal said plastic film being suffi-
ciently strong to support the weight of the liquid sealant and
capable of containing the liquid sealant while pressure is
applied to the outer walls of the reservoir to force the reser-
voir to assume a smaller volume thereby applying pressure on theliquid sealant; and a support means comprising a porous liner
adhered to the inside surface of the reservoir which liner does
not interfere with compression of the reservoir.
The present invention also provides a corrugated rigid
sheet of plastic.
The present invention further provides a kit-of-parts
comprising (a) a flexible reservoir adapted to surround a cable
splice and to contain a liquid sealant while the liquid sealant
is compressed into the cable splice comprising a plastic film
which is sufficiently strong to support the weight of the liquid
sealant and is capable of containing the liquid sealant while
pressure is applied to the outer walls of the reservoir to force
the reservoir to assume a smaller volume thereby applying
pressure on the liquid sealant and a support means comprising a
porous liner adhered to the inside surface of the reservoir which
liner does not interfere with compression of the reservoir; and
(b) a splice case.
The present invention again provides an assembly com-
prising: a cable splice; a flexible reservoir adapted to surround
a cable splice and to contain a liquid sealant while the liquid
sealant is compressed into the cable splice comprising a plastic
film which is sufficiently strong to support the weight of the
liquid sealant and is capable of containing the liquid sealant
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while pressure is applied to the outer walls of the reservoir to
force the reservoir to assume a smaller volume thereby applying
pressure on the liquid sealant and a support means comprising a
porous liner adhered to the inside surface of the reservoir which
liner does not interfere with compression of the reservoir; and
(b) a splice case.
In the practice of this invention, a flexible reservoir
formed by a plastic film is placed around a cable splice. The
reservoir is positioned so that it completely surrounds the
splice area. The ends of the reservoir are sealed to the adja-
cent cables. The reservoir has at least one opening at the top
thereof to permit filling the reservoir with a curable liquid
sealant. Preferably, such opening is virtually coextensive with
the reservoir permitting rapid filling of the reservoir. The
reservoir is of a polymeric material and preferably is of a mate-
rial which bonds or adheres to the sealant used to fill the
reservoir. The reservoir is thus formed from a plastic film,
just prior to filling with the sealant. The plastic film must be
sufficiently strong to support the weight of the liquid sealant.
A preferred plastic film is of nylon, having a thickness of about
1 to about 2 mils. Film of various thicknesses can be used. The
thickness of a particular film necessary to support the weight of
the sealant depends on the material of the film.
Support means are provided in combination with the
plastic film. Such support means is a porous liner adhered to
the inside surface of the plastic film. The liner is preferably
of a material which is compatible with the liquid sealant. The
liner can be, for example, a flexible polymeric open-celled foam
sheet of a thickness from about 0.1 inch to about 1.0 inch,
preferably from about 0.2 to about 0.5 inch. A relatively
inflexible llner such as a porous corrugated rigid sheet of plas-
tic is preferably used. When such a liner is used, it should not
prohibit or interfere with compression of the reservoir. For
example, the si~e of the liner can be such that when the reser-
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voir is positioned around the splice area, the edges of the liner
do not meet. Compression of the reservoir then forces the edges
of the liner together.
The liner is secured to the reservoir with an adhesive,
preferably a pressure sensitive adhesive. The support means can
be used alone or in conjunction with other support means. For
example, plastic support rods adhered to the outer surface of the
film may be used together with a flexible liner, if additional
support is desired.
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The curable liquid sealant used can be any
curable liquid system pourable at room temperature and
hardening, preferably to a gel-like consistency within a
relatively short period of time. Sealants of this type
are well known in the art and many are commercially
available. Liquid sealant systems used to encapsulate
cable splices are generally two-part polyurethane or epoxy
compositions. Typically, a polyurethane system comprising
a prepolymer and a curing agent are supplied separately to
be combined just prior to use.
In the practice of this invention, the curable
liquid sealant is poured into the Flexible reservoir. Air
trapped in the reservoir can be removed, if desired, by
kneading or messaging the flexible reservoir. Air bubbles
are forced to the top and can be pierced to allow air to
escape. This kneading step can be accomplished by wrapping
a first layer of tape, preferably transparent, around the
reservoir while applying slight pressure to the tape.
The reservoir, filled with liquid sealant, is
then compressed to apply pressure on the sealant. This is
accomplished by applying pressure to the outer walls of
the flexible reservoir forcing the 'reservoir to assume a
smaller volume. Such pressure forces the liquid sealant
into the interstices in the splice bundle and into the
adjacent cable. The sealant penetrates the cable core and
between the layers of the cable sheath. Compression is
maintained while the sealant hardens, preferably to a
gel-like consistency, Forming a water impenetrable seal
surrounding and throughout the splice bundle and the
adjacent cable.
The flexible reservoir can be compressed by any
suitable means. A simple expedient is to pressure wrap
the reservoir. This can be done by wrapping at least one
layer oF tape to the outside of the reservoir. The tape
is applied under tension and prefe;rably is of an elastomeric
material. As the elastomeric tape is applied, it is
stretched and elastic recovery forces continue to exert
pressure on the reservuir after it has been applied. The
tape used can be, for example, a vinyl tape, but is
preferably "double rubber" tape, an elastomeric tape
commercially available from Plymouth Rubber Co., Inc.
Other means of compressing the flexible reservoir can be
used.
Compression of the reservoir exerts pressure on
the liquid sealant in the reservoir. It is this pressure
which forces the sealant to penetrate into the interstices
of the space bundle and into the adjacent cable. The
pressure applied can be from about 3 to about 12 pounds
per square inch depending on the means used to compress
the reservoir. Pressure of up to about 1û pounds per
square inch will be adequate for most sealant/reservoir
combinations.
Penetration of the sealant some distance along
the cable core9 results in a highly desirable cable block
protecting the splice from water migrating along the cable
core or between the layers of the cable sheath. In the
practice of this invention, this is accomplished by
compressing the flexible reservoir filled with liquid
sealant. To insure that adequate penetration of the
cable core is obtained, the sheath of the cable can be
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slit or "tabbed" a short distance, generally a couple of inches,
up from the splice area. A porous insert is then positioned
under the slit cable sheath between the sheath and the cable core
providing a pathway for sealant to flow from the reservoir up the
cable. The porous insert can be, for example, a strip of net or
foam, and in a preferred embodiment, is a porous corrugated rigid
strip of plastic. Tabbing or slitting of the cable sheath in
this manner also facilitates installation of a bond clamp for
attaching a ground connector.
The present invention will be further illustrated by
way of the accompanying drawings, in which:-
Figure 1 illustrates a cable splice encompassed by a
flexible reservoir for receiving curable liquid sealant;
Figure ~ is an end view of the cable of Figure 1 show-
ing a reservoir formed from a plastic film supported by a pair of
rods;
Figure 3 shows compressing the filled reservoir by
tightly wrapping it with suitable tape; and
Figure 4 shows the completed wrapped splice enclosed
within a commercial splica case enclosure.
Figure 1 shows a splice between cables 1 and 2 which
are multi-wire communication cables each containing 300 pairs or
wire conductors. A flexible reservoir, 3, is formed from a plas-
tic film, in this case a nylon film having a porous inner linerof a corrugated rigid sheet of plastic. The reservoir is formed
by placing the nylon film around the splice area, 4, and taping
the ends of the sheet to the adjacent cable sheath. The taped
ends, 5, of the sheet form a fluid tight seal between the reser-
voir and cable. The reservoir is supported by support rods oneach side thereof, adhered to the outer surface of the film.
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Support rod, 6, on one side of the reservoir is shown in the
Figure 1. The reservoir, 3, encompasses the entire splice area,
4, which contains the individual conductors, 7, shown here ~olned
by modular connectors 8.
To more clearly illustrate formation of the reservoir,
in Figure 2, a sheet of nylon film, 10, having a porous inner
liner of a corrugated rigid sheet of plastic forms a reservoir,
3, around the splice bundle, 11, containing the individual con-
ductors, 7. Support rodsr 6, are each coated with a pressuresensitive adhesive and adhered to the outer surface of the nylon
film. The nylon film is
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positioned and secured to the cable so thst a flap, 12, is
created. The flap is folded over the opening of the
reservoir after it has been filled with liquid sealant.
After filling and closing the reservoir, the filled
reservoir is compressed, in accordance with this invention,
to force the sealant into the splice bundle and adjacent
cable core. This can be accomplished by compression
wrapping the reservoir by one or more layers of tape.
In the preferred emdodiment a first layer of trans-
parent polymeric tape is applied under light pressure. This
tape provides a fluid tight seal around the reservoir.
Application of the tape with slight compression forces the
liquid sealant to penetrate into at least the outer perimeter
of the splice bundle and forces any entrapped displaced air
to the surface of the liquid sealant. Such entrapped air
can be removed by piercing the plastic film and tape to
allow the air to escape. An additional wrap of the
transparent tape seals any holes so made. In Figure 3
this first wrap of tape, 13, is over-wrapped with a second
layer of tape, 14, which is applied under pressure to
compress the sealant-containing reservoir. This second
layer of tape is a commercially available tape made of
butyl rubber and identified as "Double Rubber" tape. As
the tape is applied under pressure it is stretched.
Since it is of an elastomeric material, it will continue
to exert additional pressure on the compressed reservoir
due to the elastic recovery forces of the stretched
material. ~ther tapes, such as vinyl tape, can be used.
The compression wrapped tapedsplice is desirably
protected against mechanical damage by enclosing the
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splice in a conventional splice case or other enclosure. A pre-
ferred enclosure is illustrated in Figure 4. In Figure 4, the
splice, 20, joining cables, 21, and 22, is enclosed in a liner,
23. The liner can be, for example, a metal, e.g., aluminum can-
ister or a thermoplastic sheet laminated to a foam layer such asthe liner disclosed in Canadian Patent No. 1,164,061. Over the
liner, 23, is a heat recovered polymeric sleeve, 24. The poly-
meric sleeve preferably is adhered to the cables, 21, and 22, by
an adhesive, preferably a hot melt adhesive, forming an environ-
mental seal around the splice. The heat-recoverable sleeve can
be a tubular sleeve or wraparound sleeve of the type known in the
art. For example a suitable wraparound heat recoverable sleeve
is described in U.S. Patent No. 3,455,336, to Ellis. Dimension-
ally recoverable sleeves which do not require heat for recovery,
such as those described in U.S. Patents Nos. 4,070,746 and
4,135,553, for example, can also be used.
The techni~ue of protecting a splice in accordance with
this invention can be used to protect splices between filled
cables and/or unpressurized air core cables. It can also be used
in a splice terminating a pressurized air core cable or connect-
ing a pressurized cable to a non-pressurized one. In this case,
the cable block prevents escape of pressurized air or other gas
from the pressurized cable. The technique can be used to protect
splices in multi-wire electric cables of any size but is particu-
larly suitable for use with larger cables, i.e., those containing
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MP0768 US1
4DO pairs or more of individual wire conductors. The
technique is particularly useful when at least one of the
cables of the splice is filled with a grease-based filling
composition.
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